Well, it wasn't just a crime of fashion, when yesterday, u.S. Customs stopped a multi-million dollar haul of counterfeit designer high heels from china before it could enter los angeles. These knockoffs are only the tip of the iceberg, a sketchy industry worth an estimated $600 billion worldwide. Phony designer swag that is not only sold on street corners but in high end shopping malls. Abc's ryan owens brings us an encore presentation. Reporter: They are the name brand fashionistas love to wear. Gucci, prad day. But for every pair of real designer jeans, there are dozens of fakes for sale. It's a booming business for the bad guys, worth an estimated $600 billion a year. Just yesterday, authorities in california confiscated more than 20,000 pairs of faux pumps, with a retail value of $18 million. These red-soled shoes were coming out of china. The genuine products are only made in italy. Reporter: The fakes cost less than $3 to make. The genuine article sell for up to 6,000 bucks. These border control guys are trained to spot the difference. But isn't just some high end fashion bust. The counterfeit business cost the u.S. Economy $250 billion a year and 750,000 american jobs. And it's not just luxury clothes and shoes. Imports range from perfume to luxury car parts to circuit boards destined for nasa. Here the long beach sea port, 14,000 containers come through every day. That's a shipment every seven seconds. With the volume of freight that we get here in los angeles, I believe that the smuggler is pretty sure if they send 20 coners, that a few of them are going to go through. Reporter: So, it's nearly impossible to catch it all. That's where chris buckner comes in. Not a cop, but a private investigator. The mileman between the police and the brands themselves. Anything that the cops don't investigate, we're really doing here at our company for those brand owners we represent. It could be real. I just need to take a better look at it. Reporter: We're with them and the cops as they enter this luxury mall in the. Kc. Just relax. We have a serf warrant. Reporter: The contraband these cops are after? Counterfeit clothes. Santa ana police officers arrest the store manager. He's accused of selling phony prada dolce and a huge stash of true religion jeans. While police put their suspect in the car outside, the brand withes behind the bust is counting the merchandise inside. So, there's not a real pair of true religion in this store that you've seen. So far, not that I've seen. This is a great hit. Reporter: Buckner shared some of his secrets on how to tell a fake. If there were authentic, it would say true religion on the inside and there's nothing on these. One of the other things, we do the smell testament they throw them in plastic bags before they are dry, through them on a container, smuggle them in. They kind of have a mildewy something to them. Reporter: Long before the cases end up at a police station, they are hatched here at investigative cop sul tants. This is our evidence. Reporter: Acting on tips, buckner's agents go undercover to gather evidence. There's a darker side than what the public knows. It's huge. It's beyond what anybody can even comprehend. Reporter: Buccaneer says counterfeiteres do a lot more than rip off designers. They say their money funds gangs, organized crime, even terrorist organizations. Police are the first to say they couldn't do it without buckner. What chris does for us is pretty much 50% of our tips and investigations. Reporter: He also goes on the raid. We'll peel off. Reporter: We tagged along for this one with t lapd. Chris waits a few blocks away to get that call. Perfect. Awesome. Reporter: This time, officers arrest this woman for selling goods out of a makeshift store in an area of downtown los angeles known as the city's counterfeit capital. Her shop may not look like much, but police say she's part of a crew making more than a half million dollars a year. About $2,000, a day. Reporter: Their evidence? Allegedly in her own handwriting. We got the subject we were looking for, recovered the merchandise. Nobody got hurt. Reporter: Last year, he took a quarter of a billion dollars worth of counterfeit goods off the street. The public doesn't really truly understand the affects. Until they stop buying, this problem is going to get bigger. Reporter: I'm ryan owens for "nightline" in orange county, california.

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